1. Field of the Invention
The present invention generally relates to ATM (Asynchronous Transfer Mode) devices, and more particularly to an ATM device which serves as an ATM NE (Network Element) provided in a subscriber line which connects connecting an ATM switch and a subscriber home. More particularly, the present invention is concerned with an ATM device which performs a PM (Performance Monitor) process, which is an OAM (Operation And Maintenance) function in the ATM layer.
Recently, a communication device that utilizes the ATM technique has been required to efficiently perform the OAM process in the ATM layer necessary for the operation and maintenance of an ATM network in order to meet various services.
In order to realize the efficiency of the OAM process in the ATM layer, it is required to provide an ATM device capable of efficiently performing the performance monitor process in the ATM layer and consuming a reduced amount of power.
2. Description of the Related Art
A conventional ATM device employs a structure as shown in FIG. 1 in order to perform the performance monitor process which is the OAM function in the ATM layer.
In the performance monitor process that is the OAM function in the ATM layer, an activation cell is defined that includes an activate cell (hereinafter also referred to Act cell), an activate confirmed cell (hereinafter also referred to as ActConf cell), and activate request denied cell (hereinafter also referred to ActDenied cell). The Act cell requests to start to execute the performance monitor process for performance test. The ActConf cell permits starting to execute the performance monitor process. The ActDenied cell denies starting to execute the performance monitor process. Also, a deactivation cell is defined which includes a deactivate cell (hereinafter also referred to as Deact cell), a deactivate confirmed cell (hereinafter also referred to as DeactConf cell), and a deactivate request denied cell (hereinafter also referred to as DeactDenied cell). The deactivate cell terminates the performance monitor process that is in progress. The deactivate confirmed cell permits terminating the performance test which is in progress. The deactivate request denied cell rejects termination of the performance test which is in progress.
The ATM device shown in FIG. 1 includes an ACT/DACT cell extractor 301, a cell information notification register 302, a CPU 303, a cell output specification register 304, an ACT/DACT cell inserter 305. The ACT/DACT cell extractor 301 extracts the activation cell and deactivation cell on the ATM network. The cell information notification register 302 temporarily stores the information of the cells extracted by the cell extractor 301 in order to notify the CPU 303 of the information. The CPU 303 controls the start and termination of the performance monitor process on the basis of the information from the register 302. The cell output specification register 304 stores the activation cell and the deactivation cell to be output under the control of the CPU 303. The ACT/DACT cell inserter 305 inserts, into the ATM network, the activation cell and the deactivation cell specified in the cell output specification register 304.
The CPU 303 is notified, via the register 302, of the cell information concerning the activation cell and the deactivation cell extracted by the ACT/DACT cell extractor 301, namely, cell information concerning the activate cell, activate confirmed cell, activate request denied cell, deactivate cell, deactivate confirmed cell and deactivate request denied cell.
The CPU 303 analyzes the received cell information, and controls the start and termination of the performance monitor process and a response to a request issued from a remote terminal.
More particularly, if the ACT/DACT cell extractor 301 extracts the activate cell, the CPU 303 determines whether the performance monitor process should be started in a channel specified by the information provided in the activate cell.
When it is determined that the performance monitor process should be started, the CPU 303 instructs the cell output specification register 304 to output the activate confirmed cell. The ACT/DACT cell inserter 305 sends the specified activate confirmed cell to the ATM network. When it is determined that execution of the performance monitor process should be rejected, the CPU 303 instructs the cell output specification register 304 to output the activate request denied cell. The ACT/DACT cell inserter 305 sends the specified activate request denied cell to the ATM network.
If the ACT/DACT cell extractor 301 extracts the deactivate cell, the CPU 303 determines whether the performance monitor process which is now in progress should be terminated in a channel specified by the information in the deactivate cell.
When the performance monitor process is allowed to be terminated, the CPU 303 instructs the cell output specification register 304 to output the deactivate confirmed cell. The ACT/DACT cell inserter 305 sends the specified deactivate confirmed cell to the ATM network. When termination of the performance monitor process is rejected, the CPU 303 instructs the cell output specification register 304 to output the deactivate request denied cell. The ACT/DACT cell inserter 305 sends the specified deactivate request denied cell to the ATM network.
When the own device sends the activate cell to the ATM network, the CPU 303 determines whether the ACT/DACT cell extractor 301 extracts the activate confirmed cell or activate request denied cell. When the activate request denied cell is extracted, the CPU 303 starts the performance monitor process from the own device. When the activate request denied cell is extracted, the CPU 303 cannot start the performance monitor process from the own device.
When the own device sends the deactivate cell to the ATM network, the CPU 303 determines whether the ACT/DACT cell extractor 301 extracts the deactivate confirmed cell or the deactivate request denied cell. When the deactivate confirmed cell is extracted, the CPU 303 terminals the performance monitor process which is in progress. When the deactivate request denied cell is extracted, the CPU 303 cannot terminate the performance monitor process that is in progress.
As shown in FIG. 2, the cell information notification register 302 of the conventional ATM device includes a memory 311 from which an interrupt request is applied to the CPU 303 when the memory 311 receives the cell information concerning the activate cell, activate confirmed cell, activate request denied cell, deactivate cell, deactivate confirmed cell and deactivate request denied cell.
However, in the conventional ATM device, the CPU is informed of all the activation cell and the deactivation cell in the performance monitor process of the ATM layer. Hence, the CPU analyzes all the activation cell and the deactivation cell, and determines, for each VP/VC channel, whether the performance monitor process should be started or terminated. Further, the CPU controls a response to each of all requests from other devices.
In practice, there is no need to process all the activation and deactivation cells extracted by the CPU, as will be described in detail later.